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Ion Channels in Nerve and Muscle of Flatworms
(Left) This is (kind of) what it looks like in the microscope when you do patch-clamp experiments. The objective is to get the glass pipette to form a very high resistance seal with the membrane of a single cell. This allows for the recording of currents across the cell membrane. (Right) This is (kind of) what I look like when I do patch-clamp experiments. Actually, I am almost never smiling.
Our laboratory has an ongoing interest in the ion channels of schistosomes and other flatworms. We are interested in these ion channels because they have much to reveal about the way schistosome muscles work, and because they could prove to be novel drug targets.
In order to study these ion channels, we use patch-clamp techniques. For the most part, we apply these techniques to individual muscle fibers dispersed from adult parasites. There are two broad types of patch-clamp experiments that we perform:
- Single Channel Recording
Measuring ionic currents across small patches of muscle membrane allows the observation of currents moving through a single ion channel This is the kind of data that results from recording ion channel activity across small patches of membrane. The sharp deflections are the opening and closing of a single ion channel--in this case, a Ca2+-dependent K+ channel from a schistosome muscle membrane. - Whole Cell Recording
Measuring ionic currents across the whole cell membrane allows the observation of ensemble currents through the entire membrane of the cell This is the kind of data that results from recording ion channel activity through whole cell membranes. Here, the data show two different outward voltage-dependent K+ currents in the schistosome muscle membrane.
Our efforts toward understanding the ion channels in flatworm nerve and muscle are currently focused on a few issues. Some of these we are actually doing, and others we are just talking about.
- Voltage-gated Ca2+ currents in flatworm muscle
For some time, the recording of voltage-gated Ca2+ currents in schistosome muscle has eluded us. Recently, we have successfully measured voltage-gated Ca2+ currents in another flatworm, the free-living turbellarian Dugesia tigrina. These currents require further characterization, because it is not yet clear how similar they are pharmacologically and physiologically to similar currents in other animals.
- Peptide-induced currents in flatworm muscle
Although we know that flatworm neuropeptides have dramatic effects on flatworm muscle, almost nothing is known about how those effects are mediated. We are characterizing the effects of flatworm peptides on the whole cell currents in flatworm muscle fibers.
- Voltage-gated currents in flatworm neurons
Very little recording has been done in any flatworm neurons. The isolated muscle cell preaprations that we use also contain many isolated nerve cells that we have yet to focus on. Undoubtedly, they will prove to have a different complement of ion channels than the muscle.
